The use of a transfer means operating on Bernoulli's principle and useful for stacking material such as freshly silvered glass mirrors where the mirrors are advancing along a conveyor is shown in co-pending application Ser. No. 450,770 filed Mar. 13, 1974, now U.S. Pat. No. 3,880,297. The apparatus disclosed in the co-pending application utilizes a single Bernoulli transfer conveyor and the path of travel of the articles on the transfer conveyor is in substantially the same direction as their path of travel on the feed conveyor which brings them from the manufacturing location to the general area of the stacking apparatus. The arrangement disclosed in the aforementioned application is limited to a batch type operation where the size of sheets on the feed conveyor in a given batch are all the same. Where sheets of different sizes are coming off the production line and randomly loaded on the same feed conveyor, a separating and classifying means is needed to arrange a plurality of stacks of different sized sheets with all sheets in any one stack being of the same size.